13.21 Highlights of What’s New in Version 35.0.1

Here is a summary of what’s changed since release 34.4.0.

13.21.1 Bug Fixes for Elements

• The order of edge transformations for the CCBEND element was revised to make more physical sense.
• A bug was fixed in the expressions for integral-based fringe field effects in QUAD and KQUAD. The bug resulted in very small inconsistencies between the matrices when K₁ →-K₁.
• Some small errors were found and fixed in the linear fringe treatment for the KQUAD and QUAD elements. Thanks to X. Huang (SLAC) for pointing out the problem.
• A bug was fixed in the NIBEND element that resulted in incorrect edge effects for ANGLE<0. This bug was apparently introduced in release 33.0.
• The SCRAPER element was not respecting changes to the DIRECTION or INSERT_FROM parameters made outside the lattice definition (e.g., using alter_elements or load_parameters). In addition, the interpretation of the INSERT_FROM=’’x’’ and INSERT_FROM=’’y’’ was incorrect, since these were supposed to correspond to a scraper inserted from both sides. Both problems were reported by forum user Youssef.
• The SPEEDBUMP element was not respecting changes to the DIRECTION or INSERT_FROM parameters made outside the lattice definition (e.g., using alter_elements or load_parameters).
• The RFCA element would bomb if no particles per present on a processor and CHANGE_T=1. This was found upon investigating a problem reported by G. Penn (ALS).
• The transport matrix for BGGEXP was being computed only to first order, which resulted in erroneous values for chromaticity, for example. This was reported by R. Linbdberg (APS).
• When CSRDRIFT elements were divided using the divide_elements command or element_divisions parameter of the run_setup command, the length was saved incorrectly to the parameters file (requested from run_setup). This was reported by Pau Gonzalez.

13.21.2 New and Modified Elements

• The CCBEND element now was a YAW parameter that permits changing the entrance and exit angles in a coordinated fashion. It also supports the FINT1, FINT2, and HGAP parameters for soft-fringe effects, as well as explicit multipoles from octupole to 18-pole (in addition to the existing support for systematic multipole errors). The multipoles at the entrance and exit can now be specified separately, using the EDGE1_MULTIPOLES and EDGE2_MULTIPOLES parameters.
• The FMULT element, which provides a general multipole with content specified by an SDDS file, now affects matrix-based computations (e.g., twiss parameters, chromaticities, and transfer matrix).
• The KSEXT element now provides a parameter for a normal quadrupole error, in addition to the existing skew quadrupole error. The utility of this was pointed out by Y.-P. Sun (APS) and X. Huang (SLAC).
• The BRANCH element now provides periodic branching, which permits modeling a periodic bypass, for example. This improvement was triggered by a question from forum user simone.dimitri.
• The global_settings command now has user overriding of default values, which means that whenever the user changes a value, it becomes the new default for any subsequent instances of the command in that run.
• The RFMODE element has additional features that help refine the agreement between the voltage obtained by rf feedback and the effective voltage seen by the beam.
• The WAKE and TRWAKE elements now accept acausal wakes, provided the user explicitly allows it with the ACAUSAL_ALLOWED parameter. This feature will be requested by R. Lindberg (APS).
• The LSRMDLTR and CWIGGLER elements now include experimental capabilities providing a transverse gradient in undulators or wigglers. In both cases, hard-to-correct residual trajectory and dispersion effects are seen, which are not yet understood. For this reason, these features are considered experimental.

13.21.3 New and Modified Commands

• The matrix_output command has two new parameters
  • print_element_data controls whether the element data is printed in addition to the matrices.
  • printout_format allows controlling the format of the printed elements.
• The analyze_map command has a new parameter, printout_format, allows controlling the format of the printed elements.
• The correct_tunes command has a new parameter, update_orbit, which allows controlling whether the orbit is updated during correction. The need for this arose from a problem encountered by I. Agapov (DESY).
• The chromaticity command has a new parameter, update_orbit, which allows controlling whether the orbit is updated during correction.
• The tracking used for matrix determination for elements, such as CCBEND, BGGEXP, and others, that rely on this, now takes advantage of parallel resources if Pelegant is used. This feature can be controlled using the newly-added parallel_tracking_based_matrices control in global_settings. The global_settings command also now offers the ability to control the number of points per phase space dimension that are used in matrix fitting, via the tracking_matrix_points parameter. The default value of this parameter has been set to 9—an increase from the minimalist value of 5 used in previous versions—in order to improve accuracy. Forum posts by J. Björklund Svensson (MAX-Lab) helped spur work on these features.
• The insert_sceffects command now supports averaging of beam size data turn-by-turn to reduce noise in transverse space charge simulation in rings, via the new averaging_factor parameter. This was suggested by V. Kornilov (GSI).

13.21.4 Changes to Related Programs and Files

• The FTABLE method for integration through 3D magnetic field maps now works in the abrat program via the -ftable commandline option. Previously, the control existed but resulted in no transformation of particles taking place.
• The program abrat now supports interpolation among multiple 2D field maps, which can be used, for example, to find the operating point in a magnet for which the field scales differently with current in different regions.
• For the longitCalcs script, the calculation of rf bucket height sometimes failed when a harmonic voltage was present; this was fixed. Also, the option to run without the GUI and put all results in a file was added.
• The makeWigglerFromBends script now includes the ability to add a gradient and specify the beam energy.
• A new program, sdds4x4sigmaproc is included that allows processing beam moments measurements from a quadrupole scan in a transport line to determine the 4x4 sigma matrix.